Objectives To determine the homeodynamic characteristics of basal insulin/glucose regulation in male rhesus monkeys. ABSTRACT:Basal levle homeodynamics of insulin/glucose regulation were studied in 20 adult male rhesus monkeys. Control monkeys (n=10) were fed ad libitum for 6-8 hr/d, while others were calorically restricted by 30% for 4.5 yr (n=10; see Am. J. Physiol. 266:E540-E547, 1994). Plasma insulin and glucose concentrations were measured in 2-min integrated samples during a 120-min baseline period and an additional 30 min period following a bolus injection of glucose (300 mg/kg body weight). Basal insulin and glucose plasma appearance and disappearance parameters were derived using spectral deconvolution techniques on the baseline plasma concentration time series. The calorically restricted animals were found to have statistically lower plasma insulin levels and plasma glucose appearance levels in conjunction with statistically longer plasma glucose clearance times and larger fractions of plasma glucose removed through metabolic clearance processes. The reduced glucose appearance coupled with the slower clearance rates resulted in similar plasma glucose levels between the two groups. These results suggest that caloric restriction influences basal insulin/glucose homeodynamics primarily through modifications of the negative-feedback branch of the regulatory control loop. Keywords caloric-restriction, insulin/glucose regulation